THE HUMAN FRAME. 81 



purpose of exciting admiration of the Creator's works, wo 

 diversify our views, and multiply our examples : but for the 

 purpose of strict argument, one clear instance is sufficient ; 

 and not only sufficient, but capable perhaps of generating a 

 firmer assurance than what can arise from a divided atten- 

 tion. 



The ginglymus, or hinge-joint, does not, it is manifest, 

 admit of a ligament of the same kind with that of the ball- 

 and-socket joint ; but it is always fortified by the species of 

 ligament of which it does admit. The strong, firm, invest- 

 ing membrane above described accompanies it in every part ; 

 and in particular joints, this membrane, v/hich is prop- 

 erly a ligament, is considerably stronger on the sides than 

 either before or behind, in order that the convexities may 

 play true in their concavities, and not be subject to slip side- 

 ways, which is the chief danger ; for the muscular tendons 

 generally restrain the parts from going further than they 

 ought to go in the plane of their motion. In the hice, 

 which is a joint of this form, and of great importance, there 

 are superadded to the common provisions for the stability of 

 the joint, two strong ligaments, which cross each other — 

 and cross each other in such a manner as to secure the joint 

 from being displaced in any assignable direction.^ "1 

 think," says Cheselden, " that the knee cannot be complete- 

 ly dislocated without breaking the cross ligaments. "f We 

 can hardly help comparing this with the binding up of a 

 fracture, where the fillet is almost wholly strapped across, 

 for the sake of giving firmness and strength to the bandage. 



* Plate II., Fig. 5. The crucial or internal ligaments of the 

 knee-jomts arise from each side of the depression between the con- 

 dyhs of the thigh-bone : the anterior is fixed into the centre, the poste- 

 rior into the back of the articulation of the tibia. This structure prop- 

 erly limits the motions of the joints, and gives the firmness requisite 

 for violent exertions. Viewing the form of the bones, we should con- 

 sider it one of the weakest and most superficial joints ; but the strength 

 of its ligaments and of the tendons passing over it, renders it the most 

 secure and the least liable to dislocation of any in the body. 



t Cheselden's Anat., ed. 7th, p. 45. 

 4* 



